1. Field
The present disclosure relates to a cooling water passage structure.
2. Description of the Related Art
In a cooling device for a water-cooled engine, an impeller of a water pump rotationally driven by the engine rotates in a pump chamber. By this rotation, cooling water in the pump chamber is centrifugally sent toward a discharge portion and supplied to a water jacket of the engine in a circulating manner.
Japanese Unexamined Patent Application Publication No. 2013-108385 describes an accessory supporting structure that supports accessories on an engine body of an internal combustion engine. The accessory supporting structure described in this document includes an accessory unit block in which a downstream-side cooling water passage extending from a pump chamber in a water pump housing in a lower part passes through a curved middle part, extends to an upper part, and reaches a cooling water communication portion communicating with a cooling water inlet in the engine body.
Japanese Patent No. 4362904 describes a cooling device for a water-cooled engine. The cooling device is configured such that when the engine is in a cold state, part of cooling water is not sent to a discharge portion of a water pump. In the cooling device described in this document, a pump housing has a passage communicating with an upper part of a pump chamber and connected to a supply and discharge unit that supplies and discharges a compressible fluid, such as air. With this configuration, part of cooling water is not supplied to a water jacket of the engine in a circulating manner, so as to improve warm-up performance of the engine.